Class 105 Polyvinyl Acetal Insulated Flat Copper Magnet Wire consisting of a copper wire as the conductor, coated with one or more layers of insulating varnish. This enameled wire has excellent mechanical strength, oil resistance, and heat resistance to hydrolysis, making it widely used in oil-immersed transformers and oil-filled motors.
Formvar enameled flat copper wire Characteristics
Oil Resistance
Heat Shock Resistance
Mechanical Strength
Application Fields
Insulating Material
The coating is based on a blend of polyvinyl acetal and phenolic resins.
NOTE—Polyvinyl acetal in this case refers to the condensation product of polyvinyl alcohol and an aldehyde and includes polyvinyl formal (Formvar).
Table 1 Dimensions
| Insulation materials | Polyvinyl Acetal |
| Thermal Class | 105 |
| Bare Wire Dimensions | width: 2mm-25mm, thickness: 0.8 – 10mm |
| Certificate | UL |
| Standard | MW 18-C |
Table 2 Properties
| Adherence and flexibility | No cracks visible in the film coating |
| Minimum Percent Elongation | MW Specification:18, 20, 36, 38, 64, 84T ≥ 0.049: 32T < 0.049:30 |
| Heat shock | No cracks visible in the film coating after 30% elongation followed by conditioning at 150 ±3°C. |
| Springback | Not greater than 5° |
Table 3 Periodic conformance tests
| Solubility | Specimens immersed in xylene shall not soften sufficiently to expose the bare conductor |
| Dielectric breakdown rated temperature | Average not less than 75% of the value required at room temperature, when tested on MW 15-C Heavy Build |
| Toluene / ethanol compatibility | No swelling or blistering in the film coating |
| Transformer oil resistance | No swelling or blistering in the film coatinga) Dielectric breakdown values shall average not less than the values in Table 4a) At least three of the five flexibility specimens shall show no cracks visible in the film coatinga) Elongation specimens shall show no swelling or blistering in the filmcoating |
| Thermoplastic flow | Median not less than 180ºC, when tested as MW 15-C Heavy Build |
Table 4 Dielectric Breakdown, Film-Insulated Rectangular and Square Magnet Wire
| Film Insulation | Minimum Breakdown Voltage | |
| Any Three of Four Values | Fourth Value | |
| Heavy | 1500 | 500 |
| Quad | 2500 | 900 |